Here at Joystiq, we love comparing the size of different things.
Ignoring for a moment the deep-seated psychological trauma behind it all, we've found this image which takes PS3 and
Revolution mockups and compares them to the Xbox 360, Xbox, PS2, slimline PS2 and Gamecube. Whew. Hit the 'Read' link
for the full image.
It looks a fairly realistic mock-up, with the Revolution winning "tiniest console by far" award, stealing the crown from the slimline PS2. However, if the Revolution really will be that small, we can't help but wonder how large the power supply will be in comparison.
[UPDATE: 4 color rebellion point out that the picture of the Revolution is misleading, as the CDROM wouldn't actually fit. They've fixed the scaling here.]